JP6826016B2 - Secondary battery ion concentration estimation method and ion concentration estimation device - Google Patents

Description

The present invention relates to a secondary battery ion concentration estimation method and an ion concentration estimation device. For example, the secondary battery ion concentration estimation method and ion concentration for estimating the concentration of redox substance ions eluted in the electrolytic solution of the secondary battery. Regarding the estimation device.

In a secondary battery using a hydrogen storage alloy containing cobalt, nickel, etc. for the electrode, the metal in the alloy is eluted into the electrolytic solution due to the corrosion of the hydrogen storage alloy. Then, the metal eluted in the electrolytic solution is reprecipitated on the positive electrode and the negative electrode. Therefore, in a secondary battery using a hydrogen storage alloy as an electrode, the self-discharge rate accelerates due to metal reprecipitation. When the self-discharge rate is increased in this way, the secondary battery cannot exhibit sufficient characteristics, and the secondary battery ends its life. Therefore, Patent Document 1 discloses an example of a method for evaluating the degree of deterioration of the secondary battery due to the acceleration of the secondary discharge rate.

The battery evaluation method described in Patent Document 1 is a method for evaluating a battery having a positive electrode, a negative electrode, and a reference electrode for measuring the potentials of the positive electrode and the negative electrode, and the potential between the positive electrode and the negative electrode is being regulated. When input voltages of different frequencies are applied between the positive electrode and the negative electrode, the response current flowing between the positive electrode and the negative electrode and the response voltage applied to the positive electrode and the negative electrode are measured, and the potential difference between the positive electrode and the reference electrode and the negative electrode are measured. And the potential difference between the reference electrode and the response current, and the impedance between the positive electrode and the reference electrode is calculated based on the response current and the potential difference between the positive electrode and the reference electrode. And, based on, the impedance between the negative electrode and the reference electrode is calculated. Then, by using the battery evaluation method described in Patent Document 1, the deterioration of the electrode during charging / discharging is determined based on the calculated impedance.

Japanese Unexamined Patent Publication No. 2016-48213

However, in the evaluation method described in Patent Document 1, although the impedances of the positive electrode and the negative electrode can be measured, it is possible to know the concentration of redox substance ions in the electrolytic solution that causes the acceleration of the self-discharge rate. There is a problem that cannot be done.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a new method for estimating the ion concentration of a redox substance in an electrolytic solution.

One aspect of the method for estimating the ion concentration of a secondary battery of the present invention is to feed the secondary battery with a charge rate adjuster for adjusting the charge rate of the secondary battery and the frequency of the measurement signal while switching the frequency at predetermined intervals. Ion concentration estimation having a negative electrode impedance measuring device for measuring the negative electrode impedance value of the secondary battery and a calculation unit for estimating the ion concentration of the oxidation-reducing substance in the electrolytic solution of the secondary battery based on the negative electrode impedance value. A method for estimating the ion concentration of a secondary battery in which the ion concentration in the electrolytic solution of the secondary battery is estimated using an apparatus, wherein a plurality of the negative electrode impedances obtained from the secondary battery adjusted to a predetermined charge rate are obtained. The spiral is prepared in advance with reference to the Nyquist diagram generated using the values, and is referred to the ion concentration estimation information showing the correspondence between the size of the spiral-shaped portion of the Nyquist diagram and the oxidation-reducing substance ion concentration. The oxidation-reducing substance ion concentration corresponding to the size of the shape portion is calculated.

Further, one aspect of the ion concentration estimation device for the secondary battery of the present invention is an ion concentration estimation device that estimates the ion concentration of the redox substance in the electrolytic solution of the secondary battery, and determines the charge rate of the secondary battery. The charge rate regulator to be adjusted and the measurement signal are output to the secondary battery while switching the frequency of the measurement signal at predetermined frequency intervals, and the negative electrode impedance value of the negative electrode of the secondary battery is measured for each frequency of the measurement signal. It has a negative electrode impedance measuring device to be used, and a calculation unit for estimating the ion concentration in the electrolytic solution of the secondary battery based on the Nyquist diagram generated by using the plurality of measured negative electrode impedance values. The calculation unit refers to the ion concentration estimation information showing the correspondence between the size of the spiral-shaped portion of the Nyquist diagram and the redox substance ion concentration, and determines the redox substance ion concentration corresponding to the size of the spiral-shaped portion. calculate.

Further, one aspect of the method for estimating the ion concentration of the secondary battery of the present invention is to give the secondary battery a charge rate adjuster for adjusting the charge rate of the secondary battery and the secondary battery while switching the frequency of the measurement signal at predetermined intervals. Then, the battery impedance measuring device that measures the battery impedance value between the positive electrode and the negative electrode of the secondary battery and the ion concentration of the oxidation-reducing substance in the electrolytic solution of the secondary battery are estimated based on the battery impedance value. The above-mentioned two, which is a method for estimating the ion concentration of a secondary battery in which the ion concentration in the electrolytic solution of the secondary battery is estimated by using an ion concentration estimation device having a calculation unit, and adjusted so as to have a predetermined charge rate. With reference to the Nyquist diagram generated by using the plurality of battery impedance values obtained from the next battery, the two predetermined battery impedance values on the Nyquist diagram in the transition frequency region of the Nyquist diagram are referred to. The difference between the real value components or the difference between the imaginary value components is calculated as the real value change amount or the imaginary value change amount, respectively, and prepared in advance, and the real value change amount or the imaginary value change amount and the oxidation. The oxidation-reducing substance ion concentration corresponding to the real value change amount or the imaginary value change amount is calculated with reference to the ion concentration estimation information indicating the correspondence with the reducing substance ion concentration.

Further, one aspect of the ion concentration estimation device for the secondary battery of the present invention is an ion concentration estimation device for estimating the ion concentration in the electrolytic solution of the secondary battery, and charging for adjusting the charge rate of the secondary battery. The measurement signal is output to the secondary battery while switching the frequency of the rate adjuster and the measurement signal at predetermined frequency intervals, and the battery impedance value between the positive electrode and the negative electrode of the secondary battery is set for each frequency of the measurement signal. It has a battery impedance measuring device for measuring, and a calculation unit for estimating the ion concentration in the electrolytic solution of the secondary battery based on the Nyquist diagram generated by using the plurality of measured battery impedance values. , The calculation unit determines the difference between the real value components or the difference between the imaginary value components between the two predetermined battery impedance values on the Nyquist diagram in the transition frequency region of the Nyquist diagram, respectively. Refer to the ion concentration estimation information calculated as the real value change amount or the imaginary value change amount, prepared in advance, and showing the correspondence between the real value change amount or the imaginary value change amount and the oxidation-reducing substance ion concentration. The oxidation-reducing substance ion concentration corresponding to the real value change amount or the imaginary value change amount is calculated.

In the ion concentration estimation method and the ion concentration estimation device of the secondary battery according to the present invention, the measured electrode or battery impedance values are acquired, the difference between the measurement points of these impedance values is obtained, and electrolysis is performed based on the difference value. The redox ion concentration in the liquid can be estimated.

According to the ion concentration estimation method and the ion concentration estimation device of the secondary battery of the present invention, it is possible to estimate the ion concentration in the electrolytic solution of the secondary battery.

FIG. 5 is a block diagram of an ion concentration estimation device for a secondary battery according to the first embodiment for estimating the ion concentration of a single battery cell. FIG. 5 is a block diagram of an ion concentration estimation device for a secondary battery according to the first embodiment for estimating the ion concentration of an assembled battery. It is a schematic diagram explaining the redox reaction in a battery cell. It is a figure explaining the difference by the presence or absence of Co ion of the Nyquist diagram of the negative electrode impedance. It is a figure explaining the difference by the presence or absence of Co ion of the Nyquist diagram of the negative electrode impedance in the vicinity of the portion where a spiral shape is generated. It is a graph which shows the change with respect to the frequency of the real value change amount between the negative electrode impedance values. It is a graph which shows the relationship between the Co ion concentration and the minimum real value change amount. It is a graph which shows the relationship between the Co ion concentration and the remaining life of a secondary battery. It is a figure explaining the difference by temperature of the Nyquist diagram of the negative electrode impedance. It is a flowchart explaining the flow of the ion concentration estimation method of the secondary battery which concerns on Embodiment 1. FIG. FIG. 5 is a block diagram of an ion concentration estimation device for a secondary battery according to a second embodiment in which an ion concentration of a single battery cell is estimated. It is a figure explaining the transition frequency domain. It is a graph explaining the relationship between a negative electrode impedance value and a Co ion concentration. It is a figure explaining the difference by the presence or absence of Co ion of the Nyquist diagram of the positive electrode impedance. It is a graph explaining the relationship between a positive electrode impedance value and a Co ion concentration. It is a graph explaining the relationship between a battery impedance value and a Co ion concentration. It is a graph explaining the relationship between the battery admittance value and the Co ion concentration. It is a flowchart explaining the flow of the ion concentration estimation method of the secondary battery which concerns on Embodiment 2.

Embodiment 1
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In order to clarify the explanation, the following description and drawings have been omitted or simplified as appropriate. In each drawing, the same elements are designated by the same reference numerals, and duplicate description is omitted as necessary.

Further, the processing described below is realized by, for example, a program executed in an arithmetic unit such as an ECU (Electronic Control Unit). This program can be stored and supplied to a computer using various types of non-transitory computer readable media. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-temporary computer-readable media include magnetic recording media (eg, flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (eg, magneto-optical disks), CD-ROMs (Read Only Memory) CD-Rs, CDs. -R / W, including semiconductor memory (for example, mask ROM, PROM (Programmable ROM), EPROM (Erasable PROM), flash ROM, RAM (Random Access Memory)). The program may also be supplied to the computer by various types of transient computer readable media. Examples of temporary computer-readable media include electrical, optical, and electromagnetic waves. The temporary computer-readable medium can supply the program to the computer via a wired communication path such as an electric wire and an optical fiber, or a wireless communication path.

FIG. 1 shows a block diagram of the ion concentration estimation device 1 according to the first embodiment. As shown in FIG. 1, the ion concentration estimation device 1 according to the first embodiment includes an ion concentration calculation device 10, a negative electrode impedance measuring device 31, and a negative electrode impedance measuring device 32.

In the block diagram shown in FIG. 1, the battery cell 20 to be measured by the ion concentration estimation device 1 is shown. The battery cell 20 is a single battery cell and has a positive electrode 21, a negative electrode 22, and a reference electrode 23. The battery cell 20 is a rechargeable secondary battery. The battery cell 20 is, for example, a nickel hydrogen battery, a lithium ion battery, or the like. Details of the battery cell 20 will be described later.

The negative electrode impedance measuring device 31 outputs an AC signal as a measurement signal, and while switching the frequency of the AC signal, the impedance between the reference electrode 23 and the negative electrode 22 of the battery cell 20 for each frequency (hereinafter referred to as negative electrode impedance). To measure. The negative electrode impedance measuring device 31 is, for example, a frequency response analysis device that analyzes the frequency response of the electrodes.

The SOC regulator 33 adjusts the charge rate (SOC: State Of Charge) of the battery cell 20 to a predetermined charge rate before measuring the negative electrode impedance of the battery cell 20.

The ion concentration calculation device 10 is, for example, an arithmetic unit such as a computer, and stores various interfaces, programs, and evaluation results for controlling an arithmetic unit that executes a program, a negative electrode impedance measuring instrument 31, a SOC regulator 33, and the like. It has a storage device (not shown). The ion concentration calculation device 10 estimates the ion concentration of the redox substance in the electrolytic solution of the battery cell 20 based on the measured value measured by the negative electrode impedance measuring device 31. The ion concentration calculation device 10 includes a measurement control unit 11, a measurement value acquisition unit 12, a calculation unit 13, and a memory 14.

The measurement control unit 11 controls the negative electrode impedance measuring device 31 and the SOC regulator 33 in a predetermined procedure. For example, the measurement control unit 11 controls the timing at which the SOC regulator 33 adjusts the charge rate of the battery cell 20 and the timing at which the negative electrode impedance measuring device 31 outputs a measurement signal to obtain an impedance value from the battery cell 20. ..

The measured value acquisition unit 12 captures the negative electrode impedance value measured by the negative electrode impedance measuring device 31, and generates a Nyquist diagram using the captured negative electrode impedance value. Such a method of impedance measurement is also called an electrochemical impedance method. Then, in the electrochemical impedance method, the frequency of the input signal is changed from a low frequency to a high frequency, and the Nyquist diagram (call call plot) in which the change in the impedance value at that time is plotted on a complex plane is obtained and analyzed inside the battery. I do.

The arithmetic unit 13 is, for example, a program execution unit that executes a program stored in a storage device such as a memory 14. The calculation unit 13 estimates the battery life based on the measured value. Specifically, the calculation unit 13 analyzes the Nyquist diagram generated by the measurement value acquisition unit 12 and estimates the ion concentration in the electrolytic solution of the battery cell 20. In the analysis process for the Nyquist diagram, the calculation unit 13 evaluates the size of the spiral waveform portion (for example, the size of the ellipse) appearing in the Nyquist diagram, and estimates the ion concentration from the size of the ellipse. Do. Specifically, in the first embodiment, two processes are performed. In the first process, the difference between the real value components between the two negative electrode impedance values on the Nyquist diagram is calculated as the real value change amount. In the following, in order to determine the size of the spiral shape appearing in the Nyquist diagram with one value, the difference between the real value components of two adjacent negative electrode impedance values on the Nyquist diagram is obtained as the real value change amount. An example of calculating the minimum real value change amount having the smallest value among the real value change amounts will be described as an example. The negative electrode impedance values used to calculate the real value change amount do not necessarily have to be adjacent to each other, and may be separated by a certain interval. In the second process, the redox corresponding to the size of the spiral-shaped portion is referred to with reference to the ion concentration estimation information prepared in advance and showing the correspondence between the size of the spiral-shaped portion and the redox substance ion concentration in the Nyquist diagram. Calculate the substance ion concentration. In the following, an example in which the minimum real value change amount is used as an index indicating the size of the spiral shape portion will be described. That is, using the information showing the correspondence between the minimum real value change amount and the redox substance ion concentration as the ion concentration estimation information, the redox substance ion concentration (for example, Co ion concentration) corresponding to the minimum real value change amount is calculated. To do.

Further, the calculation unit 13 calculates by referring to the battery life estimation information (for example, the graph of FIG. 8) showing the relationship between the redox substance ion concentration (for example, Co ion concentration) and the remaining life of the secondary battery. The remaining life corresponding to the Co ion concentration is calculated.

The memory 14 is, for example, a non-volatile memory such as a flash memory. Ion concentration estimation information and battery life estimation information are stored in the memory 14. In the first embodiment, the ion concentration estimation information includes a graph showing the relationship between the Co ion concentration in FIG. 7 and the minimum real value change amount. In addition, the battery life estimation information includes a graph showing the relationship between the Co ion concentration and the remaining life of the secondary battery. The ion concentration estimation information and the battery life estimation information are created in advance by measuring the battery sample for graph creation. The ion concentration estimation information and the battery life estimation information are not limited to the graph information, but may be a table or a mathematical formula showing the correspondence between the two values used in the analysis.

In FIG. 1, a single cell battery cell is shown as a life prediction target, but the measurement target cell may be a battery module or an assembled battery in which a plurality of single cells are connected in series. Therefore, FIG. 2 shows a block diagram of the ion concentration estimation device 2 whose life is predicted by the battery module.

FIG. 2 shows the battery module 40 to be measured. The battery module 40 is composed of a plurality of battery cells 20 connected in series. The battery module 40 has one positive electrode 41, one negative electrode 42, and a reference electrode 23 provided for each battery cell 20. The ion concentration estimation device 2 has a negative electrode impedance measuring device 32 instead of the negative electrode impedance measuring device 31. The negative electrode impedance measuring device 32 measures the negative electrode impedances of the plurality of battery cells 20 respectively, and synthesizes (for example, adds) the negative electrode impedances of the plurality of battery cells obtained by the measurement to obtain the negative electrode impedance of the battery module 40. Generated as a measured value.

Subsequently, the method for estimating the ion concentration of the secondary battery in the ion concentration estimation device 1 according to the first embodiment will be described in detail. Therefore, first, the redox reaction of the additive (conductive material) of the battery cell 20 will be described. FIG. 3 shows a schematic diagram illustrating the redox reaction in the battery cell.

Negative electrode of the nickel hydrogen battery is made of hydrogen storage alloy, as cobalt in the alloy is shown in Figure 3, an electrolytic solution repeatedly charged and discharged (e.g., an alkali aqueous solution) once dissolved cobalt ions (HCoO ₂ ^-) Is formed, and then reprecipitated on the surfaces of the positive electrode and the negative electrode. As described above, the reprecipitation of cobalt causes the acceleration of the self-discharge rate. It was found that the degree of this self-discharge rate has a phase with the cobalt ion (Co ion) concentration in the electrolytic solution. Therefore, in the method for estimating the ion concentration of the secondary battery according to the first embodiment, it is possible to estimate the Co ion concentration in the electrolytic solution and determine the period until the life of the secondary battery (remaining life). ..

Next, the relationship between the Co ion concentration and the negative electrode impedance will be described. Therefore, FIG. 4 shows a diagram for explaining the difference in the negative electrode impedance in the Nyquist diagram depending on the presence or absence of Co ions. In the Nyquist diagram shown in FIG. 4, the horizontal axis is the real value component of impedance and the vertical axis is the imaginary value component of impedance. The Nyquist diagram of the negative electrode impedance is formed by plotting the measured values on the graph for each frequency of the measured signal. As shown in FIG. 4, the Nyquist diagram gradually changes as the frequency changes. Specifically, the Nyquist diagram changes so as to include a semicircular curved portion and a linear portion.

Then, in order to verify the change in the negative electrode impedance due to Co ions, a battery in which Co ions were forcibly added to the secondary battery for verification was created, and the Nyquist diagram without Co ion addition shown in FIG. 4 was obtained. A Nyquist diagram with Co ion addition was created. In FIG. 4, the upper figure shows a Nyquist diagram without Co ion addition, and the lower figure shows a Nyquist diagram with Co ion addition. As shown in FIG. 4, the addition of Co ions causes a large change in the shape of the Nyquist diagram in which the frequency of the measurement signal ranges from 10 MHz to 10 Hz. Specifically, when the Co ion concentration in the electrolytic solution increases, a spiral waveform appears in the Nyquist diagram. This spiral waveform has a characteristic that it becomes larger as the Co ion concentration increases. Therefore, in the ion concentration estimation device 1 according to the first embodiment, the ion concentration and the remaining life of the secondary battery are evaluated focusing on the relationship between the size of the spiral shape and the ion concentration.

Next, the difference between the presence and absence of Co ions in the Nyquist diagram in the vicinity of the portion where the spiral shape is generated will be described. FIG. 5 shows a diagram for explaining the difference between the presence and absence of Co ions in the Nyquist diagram of the negative electrode impedance in the vicinity of the portion where the spiral shape is generated. As shown in FIG. 5, when there are no Co ions in the solution, the Nyquist diagram of the negative electrode impedance once decreases monotonically and changes to monotonically increase after a certain negative electrode impedance value. On the other hand, when there are Co ions in the solution, a spiral-shaped portion appears in the Nyquist diagram. As described above, the Nyquist diagram of the battery cell 20 has a significantly different shape depending on the presence or absence of Co ions. The higher the Co ion concentration in the electrolytic solution, the larger the spiral-shaped elliptical portion.

In the method for estimating the ion concentration of the secondary battery according to the first embodiment, the difference between the real value components between the adjacent negative electrode impedance values on the Nyquist diagram shown in FIG. 6 is calculated as the real value change amount, and the real value is calculated. Find the minimum real value change that minimizes the change. If there is a spiral shape, the minimum real value change amount becomes a negative value, and the larger the elliptical portion of the spiral shape, the smaller the minimum real value change amount. In FIG. 5, the magnitude of the amount of change corresponding to the measurement signal of 1 Hz and the amount of change corresponding to the measurement signal of 800 MHz among the differences in the real value components between the negative electrode impedance values are shown. The interval between the negative electrode impedance values for calculating the real value change amount may be set so that the minimum real value change amount can represent the size of the ellipse in consideration of the size of the spiral ellipse.

Here, the difference in the amount of change in the real value with respect to the frequency of the measurement signal will be described. FIG. 6 shows a graph showing the change of the real value change amount between the negative electrode impedance values with respect to the frequency. As shown in FIG. 6, the amount of change between the negative electrode impedance values increases or decreases depending on the frequency. Further, when comparing the case where Co ions are added and the case where Co ions are not added, there is a difference in the minimum value of the real value change amount. In the following description, the minimum value of the real value change amount of the negative electrode impedance value is referred to as the minimum real value change amount.

In this way, the minimum real value change amount changes depending on the difference in Co ion concentration. Therefore, FIG. 7 shows a graph showing the relationship between the Co ion concentration and the minimum real value change amount. As shown in FIG. 7, there is a certain relationship between the minimum real value change amount and the Co ion concentration. Specifically, as the Co ion concentration increases, the minimum real value change tends to decrease. In particular, when the Co ion concentration exceeds a certain concentration, the decrease in the minimum real value change amount becomes remarkable. For example, in the example of FIG. 7, when the Co ion concentration is 10 mM or more, the decrease in the minimum real value change amount becomes remarkable. In the method for estimating the ion concentration of the secondary battery according to the first embodiment, the Co ion concentration is calculated with reference to the graph showing the relationship between the Co ion concentration in FIG. 7 and the minimum real value change amount. Further, the graph showing the relationship between the Co ion concentration and the amount of change in the real value is generated by evaluating the evaluation sample in advance.

Next, the relationship between the Co ion concentration and the remaining life of the secondary battery will be described. Therefore, FIG. 8 shows a graph showing the relationship between the remaining life of the secondary battery and the Co ion concentration. As shown in FIG. 8, it can be seen that there is a certain relationship between the Co ion concentration and the remaining life of the secondary battery. Specifically, as the Co ion concentration increases, the remaining life of the secondary battery decreases. By using the Co ion concentration estimated by the method for estimating the ion concentration of the secondary battery according to the first embodiment and the graph shown in FIG. 8, a good product or a defective product of the secondary battery in consideration of the remaining life of the secondary battery. Judgment can be made. The graph showing the relationship between the remaining life of the secondary battery and the Co ion concentration shown in FIG. 8 is generated by evaluating the evaluation sample in advance.

As described above, in the method for estimating the ion concentration of the secondary battery according to the first embodiment, the negative electrode impedance value of the battery cell 20 is measured, a Nyquist diagram is generated using the negative electrode impedance value, and between the negative electrode impedance values. The minimum value (minimum real value change amount) of the real value change amount is obtained, the Co ion concentration corresponding to the minimum real value change amount is calculated, and the life of the secondary battery is estimated based on the calculated Co ion concentration. However, the negative electrode impedance value has a temperature characteristic. Therefore, when measuring the negative electrode impedance value, it is preferable to keep the temperature of the secondary battery to be measured constant.

Therefore, the temperature characteristics of the negative electrode impedance value of the secondary battery will be described. FIG. 9 shows a diagram illustrating the difference in negative electrode impedance depending on the temperature in the Nyquist diagram.

In the example shown in FIG. 9, the Nyquist diagram when the secondary battery is at 45 ° C. is shown in the upper figure, and the Nyquist diagram when the secondary battery is at 25 ° C. is shown in the lower figure. As shown in FIG. 9, when the temperature of the secondary battery is 45 ° C., the size of the spiral-shaped portion of the Nyquist diagram is larger than that at 25 ° C. That is, the amount of change in real value can be measured larger and the minimum amount of change in real value can be obtained more accurately when the temperature of the secondary battery is 45 ° C than when the temperature is 25 ° C. In addition, the life estimation accuracy can be improved by increasing the accuracy of the minimum real value change amount.

Subsequently, the ion concentration estimation procedure using the ion concentration estimation device 1 according to the first embodiment will be described. FIG. 10 shows a flowchart illustrating a flow of the ion concentration estimation method for the secondary battery according to the first embodiment.

As shown in FIG. 10, in the method for estimating the ion concentration of the secondary battery according to the first embodiment, a temperature adjustment process is performed in which the temperature of the battery is set to a preset temperature (step S0). The temperature control process is performed, for example, by putting the battery cell 20 in a constant temperature bath for a certain period of time, heating the battery cell 20 with a heater, and the like. Next, in the first embodiment, the SOC adjustment process for adjusting the charge rate of the battery cell 20 to a preset charge rate is performed (step S1). The SOC adjustment process is performed by the measurement control unit 11 giving a charge rate adjustment instruction to the SOC regulator 33.

Next, in the method for estimating the ion concentration of the secondary battery according to the first embodiment, the negative electrode impedance value is measured (step S2). In the measurement of the negative electrode impedance value, the measurement control unit 11 gives a measurement instruction to the negative electrode impedance measuring device 31. The negative electrode impedance measuring device 31 measures the negative electrode impedance value of the battery cell 20 while switching the frequency of the measurement signal according to the measurement instruction. This measurement result may be temporarily stored in the negative electrode impedance measuring device 31 and read out collectively by the measured value acquisition unit 12, or may be read out by the measured value acquisition unit 12 for each measurement. Further, in step S2, the measured value acquisition unit 12 generates a Nyquist diagram using the measured negative electrode impedance value.

Next, in the method for estimating the ion concentration of the secondary battery according to the first embodiment, the calculation unit 13 calculates the amount of change in real value between two adjacent negative electrode impedance values on the Nyquist diagram (step S3). Then, the calculation unit 13 calculates the minimum value of the real value change amount calculated in step S3 (step S4). The minimum value calculated in step S4 is the minimum real value change amount.

Next, in the method for estimating the ion concentration of the secondary battery according to the first embodiment, the Co ion concentration corresponding to the minimum real value change amount calculated in step S4 is calculated (step S5). Then, the calculated Co ion concentration is compared with the preset threshold value (step S6). When it is determined in the comparison process of step S6 that the Co ion concentration is equal to or less than the threshold value, the calculation unit 13 determines that the battery cell 20 to be inspected is a non-defective product and ends the process (step S8). On the other hand, when it is determined in the comparison process of step S6 that the Co ion concentration is larger than the threshold value, the calculation unit 13 determines that the battery cell 20 to be inspected is a defective product and ends the process (step S7).

In the flowchart shown in FIG. 10, the process of determining the non-defective product of the battery cell 20 (steps S6 to S8) is described, but the process can be completed by the process up to the estimation process of the Co ion concentration in step S5. is there.

From the above description, in the ion concentration estimation method according to the first embodiment, the negative electrode impedance value is measured while switching the frequency of the measurement signal at a predetermined frequency interval, and the real value between the two negative electrode impedance values on the Nyquist diagram. Calculate the minimum real value change amount that is the smallest of the component differences. Then, the Co ion concentration corresponding to the minimum real value change amount is estimated with reference to the ion concentration estimation information (for example, the graph shown in FIG. 7).

Thereby, in the ion concentration estimation method according to the first embodiment, the Co ion concentration in the electrolytic solution of the battery cell 20 can be estimated. Further, since there is a relationship as shown in FIG. 8 between the Co ion concentration and the life of the battery cell 20, the Co ion concentration that can be judged as a good product is obtained based on this relationship, and the obtained Co ion concentration is used as the threshold value. By doing so, it is possible to determine a non-defective product in consideration of the life of the battery cell 20 based on the Co ion concentration calculated from the measured negative electrode impedance value.

Further, the ion concentration estimation device 1 (or the ion concentration estimation device 2) that realizes the ion concentration estimation method according to the first embodiment can be realized by using a calculation function of an ECU or the like mounted on an automobile or the like. .. Further, the ion concentration estimation method according to the first embodiment can calculate the Co ion concentration without destroying the battery cell 20. For this reason, in the ion concentration estimation method according to the first embodiment, for example, for a secondary battery mounted on a hybrid vehicle or the like, a non-defective product is determined in consideration of the life of the secondary battery while using the vehicle. It can be carried out.

Embodiment 2
In the second embodiment, another aspect of the ion concentration estimation method will be described. In the ion concentration estimation method according to the second embodiment, the ion concentration of the oxidation-reducing substance in the electrolytic solution of the secondary battery is estimated based on the battery impedance value between the positive electrode and the negative electrode of the secondary battery in the transition frequency region. The inventors have found that the correlation with the ion concentration of the redox substance in the electrolytic solution appears only in the transition frequency region of the battery impedance, leading to the present invention. FIG. 11 shows a block diagram of the ion concentration estimation device 3 according to the second embodiment. In the description of the second embodiment, the same components as those described in the first embodiment are designated by the same reference numerals as those in the first embodiment, and the description thereof will be omitted.

As shown in FIG. 11, the ion concentration estimation device 3 according to the second embodiment measures the battery cell 60. In the ion concentration estimation method according to the second embodiment, since the battery impedance value between the positive electrode and the negative electrode is measured, the battery cell 60 does not need a reference electrode. Therefore, in the example shown in FIG. 11, the battery cell 60 has only a positive electrode 21 and a negative electrode 22.

The ion concentration estimation device 3 according to the second embodiment includes an ion concentration calculation device 50, a battery impedance measuring device 71, and an SOC regulator 33.

The battery impedance measuring device 71 outputs an AC signal as a measurement signal, and while switching the frequency of the AC signal, determines the impedance between the positive electrode 21 and the negative electrode 22 of the battery cell 20 (hereinafter, referred to as battery impedance) for each frequency. Measure. The battery impedance measuring device 71 is, for example, a frequency response analysis device that analyzes the frequency response of the electrodes.

The SOC regulator 33 adjusts the charge rate (SOC: State Of Charge) of the battery cell 60 to a predetermined charge rate before measuring the negative electrode impedance of the battery cell 20.

The ion concentration calculation device 50 is, for example, an arithmetic unit such as a computer, and stores various interfaces, programs, and evaluation results for controlling an arithmetic unit that executes a program, a battery impedance measuring instrument 71, an SOC regulator 33, and the like. It has a storage device (not shown). The ion concentration calculation device 50 estimates the ion concentration of the redox substance in the electrolytic solution of the battery cell 60 based on the measured value measured by the battery impedance measuring device 71. The ion concentration calculation device 50 includes a measurement control unit 51, a measurement value acquisition unit 52, a calculation unit 53, and a memory 54.

The measurement control unit 51 controls the battery impedance measuring device 71 and the SOC regulator 33 according to a predetermined procedure. For example, the measurement control unit 51 controls the timing at which the SOC regulator 33 adjusts the charge rate of the battery cell 20 and the timing at which the battery impedance measuring device 71 outputs a measurement signal to obtain an impedance value from the battery cell 60. ..

The measurement value acquisition unit 52 captures the battery impedance value measured by the battery impedance measuring device 71, and generates a Nyquist diagram using the captured battery impedance value. The Nyquist diagram is a Nyquist diagram (call call plot) in which changes in impedance values are plotted on a complex plane.

The calculation unit 63 is, for example, a program execution unit that executes a program stored in a storage device such as a memory 64. The calculation unit 63 estimates the battery life based on the measured value. Specifically, the calculation unit 53 analyzes the Nyquist diagram generated by the measurement value acquisition unit 52 and estimates the ion concentration in the electrolytic solution of the battery cell 60. In the analysis process for the Nyquist diagram, the calculation unit 53 performs two processes in the second embodiment. In the first process, the difference between the real value components of the adjacent battery impedance values determined in advance in the transition frequency region on the Nyquist diagram, or the difference between the imaginary value components is the amount of change in the real value or the imaginary value, respectively. Calculated as the amount of change. In the second process, the correspondence between the real value change amount or the imaginary value change amount and the redox substance ion concentration is shown, and the real value change amount or the imaginary value change amount is referred to with reference to the ion concentration estimation information prepared in advance. Calculate the redox substance ion concentration corresponding to.

The memory 54 is, for example, a non-volatile memory such as a flash memory. Ion concentration estimation information is stored in the memory 54. In the second embodiment, the ion concentration estimation information includes a graph showing the relationship between the Co ion concentration of FIG. 16 or FIG. 17 and the amount of change in the imaginary value. The ion concentration estimation information is created in advance by measuring a battery sample for creating a graph. The ion concentration estimation information is not limited to graph information, and may be a table or a mathematical formula that shows the correspondence between the two values used in the analysis.

In the second embodiment as well, as in the first embodiment, the measurement target may be a battery module in which a plurality of battery cells 60 are connected in series.

In the second embodiment, the analysis focusing on the impedance value in the transition frequency region on the Nyquist diagram is performed. Therefore, this transition frequency region will be described. In the method for estimating the ion concentration of the secondary battery according to the second embodiment, attention is paid particularly to the change in the Nyquist diagram in the transition frequency region occurring in the range of 10 MHz to 10 Hz.

FIG. 12 shows a diagram illustrating a transition frequency region of interest in the method for estimating the ion concentration of the secondary battery according to the second embodiment. In FIG. 12, the transition frequency region of the Nyquist diagram relating to the negative electrode impedance at which the transition frequency region becomes clearer is shown. As shown in FIG. 12, the Nyquist diagram shows a region having a correlation of a certain value or more with the arc spectrum generated due to the capacitance component of the battery cell 20, and a linear spectrum generated due to the diffusion component of the battery cell 20. It has a region having a correlation of a certain value or more (for example, a correlation coefficient of 0.99 or more) and a region in which the correlation deviates by a certain value or more from both the arc spectrum and the linear spectrum. In the method for estimating the ion concentration of the secondary battery according to the first embodiment, the frequency of the negative electrode impedance value at which the correlation value with the linear spectrum approaches a certain value or more from the frequency of the negative electrode impedance value at which the correlation value with the arc spectrum deviates by a certain value or more. Is defined as the transition frequency region.

Here, the relationship between the battery impedance value and the Co ion concentration will be described in detail. In the ion concentration estimation method according to the second embodiment, the ion concentration is estimated based on the difference in the real value component or the difference in the imaginary value component between two predetermined adjacent points on the Nyquist diagram. In the following, as an example, an example in which the impedance values obtained from the measurement signals of 100 MHz and 80 MHz included in the transition frequency region are evaluated will be described.

The battery impedance value is affected by the negative electrode impedance value and the positive electrode impedance value. Therefore, the characteristics of the negative electrode impedance value and the positive electrode impedance value will be described. The negative electrode impedance value is the same as the characteristics described in the first embodiment.

FIG. 13 shows a graph for explaining the relationship between the negative electrode impedance value and the Co ion concentration. In FIG. 13, the upper figure shows a graph showing the relationship between the difference between the real value component of the applied frequency of 100 MHz and the real value component of the applied frequency of 80 MHz and the Co ion concentration, and the lower figure shows the imaginary value component of the applied frequency of 100 MHz. A graph showing the relationship between the difference between the above and the imaginary value component at the applied frequency of 80 MHz and the Co ion concentration is shown.

As shown in FIG. 13, in the negative electrode impedance value, the amount of change in the real value component is not easily affected by the change in the Co ion concentration, and the amount of change in the imaginary value component is easily affected by the change in the Co ion concentration. Furthermore, the amount of change in the imaginary value component tends to decrease as the Co ion concentration increases.

Subsequently, the characteristics of the positive electrode impedance value will be described. FIG. 14 shows a diagram for explaining the difference between the positive electrode impedance and the Nyquist diagram with and without Co ions. In FIG. 14, the upper figure shows a Nyquist diagram of the positive electrode impedance in a state where Co ions are not added, and the lower figure shows a Nyquist diagram of the positive electrode impedance when Co ions are added.

As shown in FIG. 14, in the positive electrode impedance, a winding Nyquist diagram waveform like the negative electrode impedance does not appear. However, even in the Nyquist diagram of the positive electrode impedance, the waveform differs depending on the presence or absence of the addition of Co ions.

Therefore, FIG. 15 shows a graph for explaining the relationship between the positive electrode impedance value and the Co ion concentration. In FIG. 15, the upper figure shows a graph showing the relationship between the difference between the real value component of the applied frequency of 100 MHz and the real value component of the applied frequency of 80 MHz and the Co ion concentration, and the lower figure shows the imaginary value component of the applied frequency of 100 MHz. A graph showing the relationship between the difference between the above and the imaginary value component at the applied frequency of 80 MHz and the Co ion concentration is shown.

As shown in FIG. 15, in the positive electrode impedance value, the amount of change in the imaginary value component is not easily affected by the change in Co ion concentration, and the amount of change in the real value component is easily affected by the change in Co ion concentration. Furthermore, the amount of change in the real value component tends to increase as the Co ion concentration increases.

Subsequently, the battery impedance value will be described. FIG. 16 shows a graph for explaining the relationship between the battery impedance value and the Co ion concentration. In FIG. 16, the upper figure shows a graph of the real value change amount and the Co ion concentration between the battery impedance values acquired by the measurement signals of 100 MHz and 80 MHz among the battery impedance values, and the lower figure shows the battery impedance values. A graph showing the amount of imaginary value change between the battery impedance values acquired by the measurement signals of 100 MHz and 80 MHz and the Co ion concentration is shown.

As shown in FIG. 16, when viewed as the amount of change between two predetermined points of the battery impedance value, there is a constant relationship between the Co ion concentration and the amount of change in the real value and the amount of change in the imaginary value. It turns out that there is. In the ion concentration estimation method according to the second embodiment, the ion concentration is estimated based on the amount of impedance change between the two points.

Instead of impedance, the battery admittance value can be calculated from the measured battery impedance value, and the Co ion concentration can be estimated based on the battery admittance value. Therefore, FIG. 17 shows a graph for explaining the relationship between the battery admittance value and the Co ion concentration when the imaginary value component of the battery impedance value of FIG. 16 is converted into an admittance value. As shown in FIG. 17, by looking at the relationship between the battery admittance value and the Co ion concentration, it is possible to obtain a graph in which the measured value is enlarged. Therefore, by estimating the Co ion concentration based on the battery admittance value, it is possible to estimate the Co ion concentration with higher accuracy. Further, the estimation of the Co ion concentration based on the admittance value can also be applied to the ion concentration estimation method according to the first embodiment.

Subsequently, the ion concentration estimation procedure using the ion concentration estimation device 1 according to the first embodiment will be described. FIG. 18 shows a flowchart illustrating a flow of the ion concentration estimation method for the secondary battery according to the second embodiment.

As shown in FIG. 18, in the method for estimating the ion concentration of the secondary battery according to the second embodiment, a temperature adjustment process is performed in which the temperature of the battery is set to a preset temperature (step S10). The temperature control process is performed, for example, by putting the battery cell 60 in a constant temperature bath for a certain period of time, heating the battery cell 20 with a heater, and the like. Next, in the second embodiment, the SOC adjustment process for adjusting the charge rate of the battery cell 60 to a preset charge rate is performed (step S11). The SOC adjustment process is performed by the measurement control unit 51 giving a charge rate adjustment instruction to the SOC regulator 33.

Next, in the method for estimating the ion concentration of the secondary battery according to the second embodiment, the battery impedance value is measured (step S12). In the measurement of the battery impedance value, the measurement control unit 51 gives a measurement instruction to the battery impedance measuring device 71. The battery impedance measuring device 71 measures the battery impedance value of the battery cell 60 while switching the frequency of the measurement signal according to the measurement instruction. This measurement result may be temporarily stored in the battery impedance measuring device 71 and read out collectively by the measured value acquisition unit 52, or may be read out by the measured value acquisition unit 52 for each measurement. Further, in step S12, the measured value acquisition unit 52 generates a Nyquist diagram using the measured battery impedance value.

Next, in the method for estimating the ion concentration of the secondary battery according to the second embodiment, the calculation unit 53 determines between two adjacent points in the transition frequency region of 10 Hz or less (for example, the battery impedance value corresponding to the measurement signals of 100 MHz and 80 MHz). The real value change amount and the imaginary value change amount of are calculated (step S13). Then, the calculation unit 53 calculates the Co ion concentration corresponding to the real value change amount calculated in step S13 with reference to the graph shown in FIG. 16 (step S14). Further, the calculation unit 53 calculates the Co ion concentration corresponding to the amount of change in the imaginary value calculated in step S13 with reference to the graph shown in FIG. 16 (step S15).

Next, in the method for estimating the ion concentration of the secondary battery according to the second embodiment, the Co ion concentration calculated in step S14 or step S15 is compared with the preset threshold value (step S16). When it is determined in the comparison process of step S16 that the Co ion concentration is equal to or less than the threshold value, the calculation unit 53 determines that the battery cell 60 to be inspected is a non-defective product and ends the process (step S18). On the other hand, when it is determined in the comparison process of step S16 that the Co ion concentration is larger than the threshold value, the calculation unit 53 determines that the battery cell 60 to be inspected is a defective product and ends the process (step S17).

When the battery impedance characteristic of the battery cell 60 is as shown in FIG. 16, the determination process in step S16 uses the Co ion concentration derived from the relationship between the amount of imaginary value change and the Co ion concentration. Is preferable. This is because the change with respect to the Co ion concentration is larger in the imaginary value change amount. This is because the estimation accuracy of the Co ion concentration is improved by using a component having a large change with respect to the Co ion concentration.

From the above description, in the ion concentration estimation method according to the second embodiment, the battery impedance value is measured while switching the frequency of the measurement signal at a predetermined frequency interval, and a predetermined real value change amount between two adjacent points and a predetermined real value change amount. Calculate at least one of the imaginary value changes. Then, the Co ion concentration corresponding to the real value change amount or the imaginary value change amount is estimated with reference to the ion concentration estimation information (for example, the graph shown in FIG. 16).

In the second embodiment, the Co ion concentration is estimated based on the battery impedance value measured between the positive electrode and the negative electrode of the battery cell 60. As a result, in the second embodiment, there is an effect that it is not necessary to provide the reference electrode in the battery cell 60.

The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit. In the above embodiment, the case where the redox substance is cobalt (Co) has been described by taking a nickel hydrogen battery as an example. However, the redox substance is not limited to this, and the present invention can be applied as long as it is a substance that reacts at both the positive electrode and the negative electrode. For example, in the case of a lithium ion storage battery, iron (Fe) and the like can be mentioned as the redox substance.

1 Ion concentration estimation device 2 Ion concentration estimation device 3 Ion concentration estimation device 10 Ion concentration calculation device 11 Measurement control unit 12 Measurement value acquisition unit 13 Calculation unit 14 Memory 20 Battery cell 21 Positive electrode 22 Negative electrode 23 Reference electrode 31 Negative electrode impedance measuring device 32 Negative electrode impedance measuring device 33 SOC regulator 40 Battery module 41 Positive electrode 42 Negative electrode 50 Ion concentration calculation device 51 Measurement control unit 52 Measurement value acquisition unit 53 Calculation unit 54 Memory 60 Battery cell 71 Battery impedance measuring instrument

Claims (16)

A charge rate regulator that adjusts the charge rate of the secondary battery,
A negative electrode impedance measuring device that measures the negative electrode impedance value of the secondary battery by giving the frequency of the measurement signal to the secondary battery while switching the frequency at predetermined intervals.
The ion concentration in the electrolytic solution of the secondary battery is estimated using an ion concentration estimation device having a calculation unit for estimating the ion concentration of the redox substance in the electrolytic solution of the secondary battery based on the negative electrode impedance value. It is a method for estimating the ion concentration of a secondary battery.
Refer to the Nyquist diagram generated using the plurality of negative electrode impedance values obtained from the secondary battery adjusted to a predetermined charge rate.
The redox substance ion concentration corresponding to the size of the spiral-shaped portion is determined by referring to the ion concentration estimation information prepared in advance and showing the correspondence between the size of the spiral-shaped portion and the redox substance ion concentration in the Nyquist diagram. A method for estimating the ion concentration of a secondary battery to be calculated. The method for estimating the ion concentration of a secondary battery according to claim 1, wherein the size of the spiral-shaped portion is determined based on the difference between the real value components of the two negative electrode impedance values on the Nyquist diagram. The size of the spiral-shaped portion is determined based on the minimum real value change amount, which is the smallest of the differences between the real value components of the two negative electrode impedance values on the Nyquist diagram.
The ion concentration estimation method for a secondary battery according to claim 1, wherein the ion concentration estimation information indicates a correspondence between the minimum real value change amount and a redox substance ion concentration. The size of the spiral-shaped portion is determined based on the minimum real value change amount, which is the smallest of the differences between the real value components of the two adjacent negative electrode impedance values on the Nyquist diagram.
The ion concentration estimation method for a secondary battery according to claim 1, wherein the ion concentration estimation information indicates a correspondence between the minimum real value change amount and a redox substance ion concentration. The Nyquist diagram is generated by plotting a negative electrode admittance value calculated from the negative electrode impedance value, and the size of the spiral-shaped portion of the Nyquist diagram is determined based on the negative electrode admittance value. The method for estimating the ion concentration of a secondary battery according to any one of the above items. The method for estimating the ion concentration of a secondary battery according to any one of claims 1 to 5, wherein a temperature adjustment process for setting the secondary battery to a predetermined temperature is performed before acquiring the negative electrode impedance value. Claims 1 to 6 for calculating the remaining life corresponding to the calculated redox ion concentration with reference to the battery life information showing the relationship between the redox substance ion concentration and the remaining life of the secondary battery. The method for estimating the ion concentration of a secondary battery according to any one of the items. It is an ion concentration estimation device that estimates the ion concentration of redox substances in the electrolytic solution of a secondary battery.
A charge rate regulator that adjusts the charge rate of the secondary battery,
A negative electrode impedance measuring device that outputs a measurement signal to the secondary battery while switching the frequency of the measurement signal at predetermined frequency intervals and measures the negative electrode impedance value of the negative electrode of the secondary battery for each frequency of the measurement signal.
It has a calculation unit for estimating the ion concentration in the electrolytic solution of the secondary battery based on the Nyquist diagram generated by using the plurality of measured negative electrode impedance values.
The calculation unit
The ion concentration for calculating the redox substance ion concentration corresponding to the size of the spiral-shaped portion by referring to the ion concentration estimation information showing the correspondence between the size of the spiral-shaped portion and the redox substance ion concentration in the Nyquist diagram. Estimator. The calculation unit is requested to calculate the remaining life corresponding to the calculated redox substance ion concentration by referring to the battery life information showing the relationship between the redox substance ion concentration and the remaining life of the secondary battery. Item 8. The secondary battery ion concentration estimation device according to Item 8. A charge rate regulator that adjusts the charge rate of the secondary battery,
A battery impedance measuring device that applies the frequency of the measurement signal to the secondary battery while switching the frequency at predetermined intervals and measures the battery impedance value between the positive electrode and the negative electrode of the secondary battery.
The ion concentration in the electrolytic solution of the secondary battery is estimated using an ion concentration estimation device having a calculation unit for estimating the ion concentration of the redox substance in the electrolytic solution of the secondary battery based on the battery impedance value. It is a method for estimating the ion concentration of a secondary battery.
Refer to the Nyquist diagram generated using the plurality of battery impedance values obtained from the secondary battery adjusted to a predetermined charge rate.
In the Nyquist diagram, the difference between the real value components or the difference between the imaginary value components between the two predetermined battery impedance values on the Nyquist diagram in the transition frequency region is the amount of change in the real value or the difference between the imaginary value components, respectively. , Calculated as the amount of imaginary value change,
Oxidation corresponding to the real value change amount or the imaginary value change amount with reference to the ion concentration estimation information prepared in advance and showing the correspondence between the real value change amount or the imaginary value change amount and the oxidation-reducing substance ion concentration. A method for estimating the ion concentration of a secondary battery for calculating the ion concentration of a reducing substance. The transition frequency region includes the Nyquist diagram and the two from the measurement frequency of the battery impedance value at which the correlation value between the Nyquist diagram and the arc spectrum generated due to the capacitance component of the secondary battery deviates by a certain value or more. The method for estimating the ion concentration of a secondary battery according to claim 8, wherein the correlation value with the linear spectrum caused by the diffusion component of the secondary battery approaches a certain value or more, which is a frequency region up to the measurement frequency of the battery impedance value. .. The secondary battery according to claim 8 or 9, wherein the battery impedance value used for calculating the real value change amount or the imaginary value change amount is two adjacent battery impedance values on the Nyquist diagram. Ion concentration estimation method. The Nyquist diagram is generated by plotting a battery admittance value calculated from the battery impedance value, and the real value change amount or the imaginary value change amount is calculated based on the battery admittance value. The method for estimating the ion concentration of a secondary battery according to any one of 10. Claims 10 to 13 for calculating the remaining life corresponding to the calculated redox ion concentration with reference to the battery life information showing the relationship between the redox substance ion concentration and the remaining life of the secondary battery. The method for estimating the ion concentration of a secondary battery according to any one of the items. An ion concentration estimation device that estimates the ion concentration in the electrolyte of a secondary battery.
A charge rate regulator that adjusts the charge rate of the secondary battery,
The measurement signal is output to the secondary battery while switching the frequency of the measurement signal at predetermined frequency intervals, and the battery impedance value between the positive electrode and the negative electrode of the secondary battery is measured for each frequency of the measurement signal. With a measuring instrument
It has a calculation unit for estimating the ion concentration in the electrolytic solution of the secondary battery based on the Nyquist diagram generated by using the plurality of measured battery impedance values.
The calculation unit
In the Nyquist diagram, the difference between the real value components or the difference between the imaginary value components between the two predetermined battery impedance values on the Nyquist diagram in the transition frequency region is the amount of change in the real value or the difference between the imaginary value components, respectively. , Calculated as the amount of imaginary value change,
Oxidation corresponding to the real value change amount or the imaginary value change amount with reference to the ion concentration estimation information prepared in advance and showing the correspondence between the real value change amount or the imaginary value change amount and the oxidation-reducing substance ion concentration. A secondary battery ion concentration estimation device that calculates the ion concentration of a reducing substance. The calculation unit is requested to calculate the remaining life corresponding to the calculated redox substance ion concentration by referring to the battery life information showing the relationship between the redox substance ion concentration and the remaining life of the secondary battery. Item 5. The secondary battery ion concentration estimation device according to Item 15.

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